It isn’t a “granular” definition - read her wiki page. She stitched suicide vests, so they couldn’t remove the explosives without going “boom”. She enforced “morality” laws. She carried an AK with her. She was regarded as an enforcer. She tried to recruit other girls into ISIS.
She got lured into joining by watching beheading videos and the luxuries of living as a terrorist. She literally said “I still hold ‘some’ of the UK’s values”. She didn’t regret going to Syria. She excused terrorist attacks. She excused rape in ISIS. She has no remorse for what she did while there.
This is a textbook case of a law working. The only difference between her, and other people deprived of citizenship for similar things, is that she has a PR agency.